Birds are visible. Birds are beloved. Birds get the frequent attention of millions who note their appearance at feeders, their passage during migration, and their presence in local woods or parks. Birds, though they may appear individually delicate, are a diverse, tough, flexible group—feathered dinosaurs—who have weathered every change of conditions, survived every extinction event, and fended off competitors for 150 million years. When birds are in trouble, everything is in trouble. And birds are in trouble.
A report published this week in Science looks specifically at birds in North America, and what it finds is a precipitous decline. Both diversity and sheer numbers of birds are down sharply, across the whole range and across very different groups. Since 1970, the total number of birds in North America has dropped by 29%—about 3 billion birds lost in under 50 years.
If you father tells you there used to be more ducks on the nearby lake, he’s right. If your grandmother complains that birdsong has vanished from her neighborhood, it’s not because her hearing has decline. As the scientist put it, what we’re seeing is an “avifaunal collapse.”
While the popularity of birding, from backyard feeder counts to dedicated surveys, makes it possible to get a good handle on what’s happening with this particular group of animals, there’s no reason to think that what’s happening in the environment is especially targeting birds. Scientists are aware that amphibians—frogs, toads, and salamanders—have been all but eradicated in some areas. Bats have also been decimated by disease, habitat loss, and pollution. All those groups have been hit with a sharp drop in the number of insects in the environment. If a bird or bat or frog depends on a specific kind of insect for its food source, and that insect is gone, so are they.
What may be most shocking about the numbers in the Science article is just how universal they are. Even species that are as ubiquitous as robins and sparrows had sharp declines. The most common birds, are much less common than they were a few years ago. That was true across the great majority of the 529 species examined in the study. And the decline of those common birds is likely to have a much greater impact as the ecosystem tumbles.
Birds that exist across the country in their millions, or hundreds of millions, do so because they occupy a niche that is just as common, equally widespread. The falling numbers of these birds shows that this isn’t just about specific conditions hitting “specialists” who live in strict conditions or dine on very limited fare. It is hard to be more of a generalists in either living conditions or diet than blackbirds. But blackbirds are down.
As much as people enjoy watching birds for their colorful plumage and complex behaviors, there is much more to them than the joy they bring by their presence. Many plants depend on birds to spread their seeds. Birds are second only to insects in pollinating flowers. And many insect-eating birds chow down on exactly the kind of insects that bring bites and disease to humans. Their loss hurts us aesthetically, and in the stomach, and in the blood.
The suspected culprits for the decline are no great surprise—loss of habitat and chemicals in the environment. Pesticides have not just given us shinier apples, but eliminated insects that fed sparrows. Herbicides have wiped out plants whose seeds were staples for dozens of species. Both have run into waters and destroyed populations of fish and frogs that fed shorebirds.
There have been five great extinction events—events where the majority of living species were wiped out—over the last 500 million years. That includes the one that happened as an asteroid plowed into Earth around 66 million years ago. Even though we often mark that event as the “end of the age of dinosaurs,” that asteroid really couldn’t wipe out all the dinosaurs.
But we’re giving it a solid try.